The present invention relates to fluid injection systems and the detection of abnormalities in fluid injection conduits.
In the area of patient intravenous fluid injection, a catheter and needle are typically placed into a patient vein with the needle tip aperture located within the vein so as to permit infusion of the applied medication. In typical usage, the IV infusion is set up and left to operate for extended periods without attendance. In this condition it is important to be able to detect the presence of abnormalities in the fluid delivery system. More important to the safe and proper use of the infusion system is the ability to distinguish several possible abnormalities one from the other.
Additionally there are applications for insertion of catheters and associated instrumentation into patient veins for placement up or down the vein to locations such as heart cavities or elsewhere for more direct detection or treatment. In such cases it is important to be able to monitor the progress of the catheter to determine whether it progresses up the vein correctly or is encountering various difficulties along the way such as kinking, clotting, sticking on a vein wall, and to know which of the difficulties is being encountered.
In one embodiment for a catheter condition detection in the prior art as represented by U.S. Pat. No. 4,710,163, there is shown a system in which an infusion pump is modulated to produce a flow variation that is used to detect a blockage. Such a system adds great complexity to the pump, fails to provide a range of abnormalities that can be independently detected, and limits flexibility to the only situations where that pump can be used.